Dr. Hugh Ross has released another informative article examining some of the properties the Milky Way galaxy possesses which make it suitable for life. People who believe life is common throughout the Universe often point to the vast number of galaxies to support their position. But the devil is in the details.
Galaxies comes in all shapes and sizes – even colors. Some galaxies are blue, which indicate they are younger, hotter and aggressively forming news stars and solar systems. Other galaxies are red, which indicates they are older, cooler and ending their star formation period. The Milky Way is green, which is rare, and it suggests a moderate star formation rate.
Green is good for life forming planets. A blue galaxy will introduction flares, ultraviolet and x-ray radiation that are too intense for life. Red galaxies will also introduce flares that are too intense for life, as well as expose planets to too many nova and supernova explosions. But green galaxies are just right.
The article goes on to discuss the stability and symmetry of the spiral arms of our galaxy which is partly made possible due to the large number of yellow stars it posses and significant quantity of blue stars. If the Milky Way were blue or red, it wouldn’t be able to maintain it’s clean spiral structure which is essential for life.
Other properties such as the under-luminosity of the Milky Way (which protects Earth from radiation), the unique presence of the Large and Small Magellanic Clouds and relatively benign merger history are also important to sustaining life. Of the 200 to 400 billion estimated galaxies in the Universe, how many have the right age, temperature, structure, shape, color, star formation history, neighboring galaxies, etc… to support life? Apparently not as many as one might initially think.